High-temperature superconducting (HTS) materials, such as yttrium-barium-copper-oxide (YBCO), have been used to make thin film superconductor devices and wires. Thick (i.e., >1 μm) HTS films, having a higher critical current (Ic), are preferred in applications requiring high current carrying capability, e.g., power transmission and distribution lines, transformers, fault current limiters, magnets, motors, and generators. With conventional solution-based techniques, thicker superconducting films are formed of multiple layers of HTS thin films, each having a thickness no greater than 1 μm.
Superconducting thin films may be deposited on buffered or unbuffered substrates by a variety of techniques including decomposition of trifluoroacetate-based metal organic precursors. Precursor decomposition is the slowest and most critical step in the manufacturing of HTS thin films. When a precursor film undergoes decomposition, a significant volume change occurs, generating stresses within the film. If uncontrolled, these stresses can cause extensive cracking in the resulting intermediate film, which in turn leads to failure of forming a HTS coating with a high Ic. Thus, it is important to accommodate these stresses. One way to achieve this is control the decomposition rates of different precursors by careful selection of, e.g., decomposition temperature, line-speed, gas flow rate, and gas composition. See U.S. Pat. Nos. 6,669,774 and 6,797,313.
As it requires multiple coating and decomposition steps to produce a thick HTS film formed of multiple layers, it is difficult to greatly reduce the processing time without compromising the quality of HTS film, e.g., an Ic drop. Thus, there is a need to develop new methods for making thick films formed of a single layer of HTS materials.